Anisotropy

Anisotropy is the absence of isotropy. When we say that a certain structure is anisotropic, we mean that it is not equal in every direction. A blank, infinite piece of paper, for example, is isotropic: an ant on it cannot know which direction it’s going. A striped piece of paper, however, is anisotropic, because it’s possible to know whether one is going upwards or sideways. In Physics, when one talks about the isotropy of space, one means it looks roughly the same, independently of the direction. This simplification is of great use for developing workable cosmological models.